During Release 12, the LTE standard has been extended with support of device-to-device (D2D) (specified as “sidelink”) features targeting both commercial and Public Safety applications. An example application enabled by Rel-12 LTE is device discovery, where devices are able to sense the proximity of another device and associated application by broadcasting and detecting discovery messages that carry device and application identities. Another example application is direct communication based on physical channels terminated directly between devices.
One of the potential extensions for the device to device work consists of support of vehicle-to-anything-you-can-imagine (V2x) communication, which includes any combination of direct communication between vehicles, pedestrians and infrastructure. V2x communication may take advantage of a network infrastructure, when available, but at least basic V2x connectivity should be possible even in case of lack of coverage. Providing an LTE-based V2x interface may be economically advantageous because of the LTE economies of scale, and it may enable tighter integration between communications with the network infrastructure (V2I), vehicle-to-pedestrian (V2P) communications, and vehicle-to-vehicle (V2V) communications, as compared to using a dedicated V2x technology.
V2x communications may carry both non-safety and safety information, where each of the applications and services may be associated with specific requirements sets, e.g., in terms of latency, reliability, capacity, etc. ETSI has defined two types of messages for road safety: Co-operative Awareness Message (CAM) and Decentralized Environmental Notification Message (DENM).
The CAM message is intended to enable vehicles, including emergency vehicles, to notify their presence and other relevant parameters in a broadcast fashion. Such messages target other vehicles, pedestrians, and infrastructure, and are handled by their applications. CAM messages also serve as active assistance to safety driving for normal traffic. The availability of a CAM message is indicatively checked for every 100 ms, yielding a maximum detection latency requirement of less than or equal to 100 ms for most messages. However, the latency requirement for a pre-crash sensing warning is 50 ms.
The DENM message is event-triggered, such as by braking, and the availability of a DENM message is also checked for every 100 ms. The requirement of maximum latency is less than or equal to 100 ms.
The package size of CAM and DENM messages varies from 100+ to 800+ bytes, and the typical size is around 300 bytes. The message is supposed to be detected by all vehicles in proximity.
The SAE (Society of the Automotive Engineers) also defined the Basic Safety Message (BSM) for Dedicated Short Range Communications (DSRC), with various messages sizes defined. According to the importance and urgency of the messages, the BSMs are further classified into different priorities.
The geographical distribution of V2x communication follows the distribution of the road infrastructure, which may not coincide with that of the telecommunications infrastructure (e.g., the cells). Consequently, V2x traffic may be unevenly spread over each network cell. Existing distributed resource allocation algorithms for V2x applications yield a low degree of spatial reutilization, which precludes the redeployment of unused resources for other applications. Thus, there is a need for an improved resource allocation scheme.